Influences of the presence of char layer on flame spreads over wood with different thermal thickness.

A series of ISO 5658-2 flame spread experiments on Douglas-fir specimens were carried out to investigate the relationship between flame spread characteristics and thermal thickness of solid combustibles, which is greatly influenced by char formation during combustion. Computations using the fire dynamics simulator (FDS) were performed to recreate these experiments. The measured and calculated flame spread characteristics were then compared and analyzed based on thermal thickness and char residue ratio. The results clearly show that the effects of char formation on the surface of wood during combustion are more noticeable in thermally thick regimes than in thermally thin regimes. The findings provide an important foundational understanding of the influence of char formation on solid combustibles on flame retardant properties, which has not previously been studied. [ABSTRACT FROM AUTHOR]